-LRB- CNN -RRB- -- My friend Brian Hull and I were both born 40 years ago today .

Our lives overlapped for six years , from those first terrifying weeks of seventh grade through high school graduation . Then , like many of the friends you meet in those horrible , wonderful years , I never saw or talked to him again .

We did n't start out as friends ; we started out as nothing . He was a guy in my math class who wore nice clothes and hung out with the other cool kids at lunch . I ran in different circles and had zero interaction with him up until the day we found out we had the same birthday .

That day , our math teacher , Mr. Sweitzer , had us go around the room and say our birthdays out loud to demonstrate a point about probability , that in a classroom of 30 people , there 's a good chance that two of them have the same birthday . In our class , it was me and Brian . Once we discovered this connection , I turned to look at him , and he gave me a slight head nod as he raised a confident fist in the air and let out one of his characteristic low chuckles . After class , we talked briefly about where we were born and at what time of day .

That day , we became birthday friends . Over time , we became friends .

Brian was an easy person to like . He was a quiet and stoic leader , which on first blush could make him seem aloof or arrogant . Though he could be stingy with his words and often spoke in a low , monotone voice that adults often interpret as deep apathy , he was articulate and witty and thoughtful about the many things in the world that interested him . On top of that , he was really smart . One day in ninth-grade Spanish class , he rebelled against Miss Kahn 's selected topic of conversation and instead suggested that we discuss the ongoing battle over Robert Bork 's nomination to the Supreme Court . In Spanish .

I admired how he was passionate about a wide range of things , like politics and philosophy and religion and the environment and the Grateful Dead . I admired how he never seemed to have an unsure or awkward moment . To this day , when I 'm in an uncomfortable social situation , I 'll wonder , `` How would Brian Hull handle this ? ''

I saw this quality in him tested , maybe even stretched to the limit , in our junior year . Brian and I were still in many of the same classes , but for whatever reason , he seemed less and less engaged in school . I imagine that a common refrain in the teachers ' lounge when it came to Brian was that he was smart but did n't apply himself . He missed a lot of classes ; I do n't know why . I just assumed at the time that it was because being popular was a full-time job . From what I could piece together from movies and TV , it looked exhausting .

Whatever the reason , the absences and missed assignments were taking a toll , and things came to a head in English class . I overheard the teacher tell him how serious the situation had become , and how critical the upcoming exam on `` Oedipus Rex '' would be . I knew he had n't read the book and had n't been in enough of the class discussions to fake it , so I offered to study with him . I had my own problems at the time , but helping him was a welcome distraction , a concrete action I could take when I felt powerless over other parts of my life . So we went over every mother-loving detail of that miserable Greek tragedy .

In the movie version , this is where I would say that he aced that exam and got his act together and excelled at everything he did thereafter , and it was all because of a little help from his friend who was born on the same day .

The reality is that I have no recollection of how he did on that exam or how he did in English or in any of his other classes that year , or what role I might have played in refocusing him . Still , inside the pages of my yearbook , he wrote a note thanking me for all the help .

I do know that he eventually pulled things together and that we both survived high school and moved on with our lives . I do n't remember the last time I saw him or the last conversation we had . But I knew he had started college and focused on his loves of both philosophy and the environment .

On the night of October 22 , 1995 , Brian James Hull was struck and killed by a drunken driver as he and his roommate walked to a convenience store to buy charcoal . His friend was also killed . By that time , I had graduated from college and was living out-of-state . I missed the news . When I did finally hear , after the initial shock , my mind kept drifting to all the birthdays he was n't going to have .

Brian was only 22 when he died . This is the 18th birthday he 's missed . I 've thought about him at each one . I think about whatever is going on in my life at the time , and how trivial it all suddenly seems .

I think about the man Brian would have become . By age 40 , Brian Hull might have become a university professor or a successful entrepreneur or maybe an author . His argumentative streak would have made him a great lawyer . He 'd probably be married , and maybe a father of kids who would quickly come to appreciate the Grateful Dead . And he would have excelled at all these things .

When I think about him today , I wish I had gotten to know him better . He wrote in my yearbook junior year , `` I 'll give you a call over the summer , and maybe we can go play a championship-like tennis match at a court within close proximity . Have a thoroughly stimulating summer , and I hope to see you over it . ''

We never played tennis , and we never saw each other over that summer . Life has a way of intervening .

Earlier this month , I visited Brian 's final resting place for the first time to pay my respects in person . It 's a very strange feeling to see your date of birth written on a headstone . It gives you a sense of your own mortality . It makes you think about the life you have and how you are living it .

When I think about him today , I wonder who the other Brians in my life are right now -- am I squandering any opportunities to play tennis with them or see them over the summer ? And because of Brian , I try to make an effort to do something about it , albeit sometimes with more gusto than others .

All these years since our friendship began in Mr. Sweitzer 's class , I thank him for that lesson .

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CNN 's Robert Yoon shared a birthday with his schoolmate Brian Hull

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Yoon thought they had little in common , but a friendship slowly formed

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The pair promised to stay in contact after school ended but life got in the way

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When Hull died at age 22 , Yoon realized friendship is a treasure to be preserved